Which combination is used to fill joints in tilt-up panels?

• A. Silicone (most common), compound
• B. Silicone (most common), compound, and modified grout
• C. Modified grout only
• D. Epoxy resin

Answer: (B)

Joints between tilt-up panels must stay watertight while absorbing movement from temperature changes and shrinkage. The best approach uses a flexible silicone sealant in the joint because silicone remains elastic over a wide range of temperatures and bonds well to concrete, keeping out water while allowing panel movement. Behind the sealant, a backing material or compound helps define the correct sealant depth and provides a stable surface for adhesion. For joints that need some structural fill and load transfer between panels, a modified cementitious grout is used to fill the lower portion of the joint, contributing to stiffness and ensuring transfer of forces where panels meet. Epoxy resin is too rigid for movement joints, and using only modified grout wouldn’t provide a watertight seal or accommodate movement.